Conteol system



Mafch 8, 1949. E. G. BAILEY ETAL Re. 23,087

CONTROL SYSTEM Original Filed Oct. 18, 1943 5 Sheets-Sheet J.

DAISIES c I [L' J]| g 2|0 j v 1/- 2n w 1 z 5 203 5 207 was 1 205 i 9.

: Y 17,] [I I II [Ill 1 I ZIZ 201 ,1 FIG. 7

FIG. 2

ZSnoentors ERVI'N s. BAILEY AND PAUL S. DICKEY 5 shaets -shee t 2 March8, 1949. E. G. BAILEY ET AL common SYSTEM Original Filed Oct. 1s. 194sFIG,

FUEL

inventors ERVIN G. BAILEY AND PAUL S. DICKEY @gml I Gttomeg FIG.

March 8, 1949.

E. G. BAILEY ET AL CONTROL SYSTEM AIR ERVIN ,6. BAILEY AND PAUL S.DICKEY Simentors FIG. 5

15 1949- G. BAILEY:

-opmno1. SYSTEM 5 Sheets-Sheet 4 Origi al Filed Oct 18, 1943 ZSnocntonERVIN s BAILEY AND PAUL S.DICKEY March-8, 1949. E. G. BAILEY ET ALCONTROL SYSTEM 5 Sheets-Sheet 5 Original Filed Oct. 18. 1943 Zinnentorsattorney ERVIN G. BAILEY mo PAUL s. DICKEY Reiuued Mar. 8, 1949 CONTROLSYSTEM Ervin G. Bailey, Easton, Pa., and Paul S. Dickey,

East Cleveland, Ohio, assignors, by mesne as-.

signments, to The Babcock & Wilcox Company, New York, N. Y., acorporation of New Jersey Original l lo. 2,417,049, dated March 11,1947,Se-

rial No. 506,630, October 18, 1943,. Application for reissue February12, 1948, Serial No. 7,924

35 Claims. '(Cl. 263-19) The present invention relates in general to theoperation and control of fluid heaters of the type in which the heattransfer medium consists of a fluent gas-pervlous mass 01 refractorymaterial which is first heated by the passage of a heating fluid in heattransfer relation therewith and then cooled by contact with a secondfluid to be heated; and more particularly to fluid heaters of thecharacter illustrated and described in which the fluent mass of heattransfer material moves downwardly through superposed heating andcooling chambers connected by a neck or throat of reduced flow area.

The general object of our invention is the provision of a method ofanapparatus-for operating and controlling fluid heating apparatus of ,thecharacter disclosed for continuously heating. the fluid under pressureat high capacities to a F., and with a. relatively high overall thermalefficiency.

A further object is the provision of a method and apparatus forautomatically controlling the operation of such a fluid heaterto-provide continuous uniform leaving temperature of the heated materialunder continuous or varying rates of operation as may be desired.

, Another object of our invention is the provisionof method andapparatus for safely operating such a fluid heater at different, ratesof operation. Such a system includes protective and interlock apparatussensitive to emergency or adverse conditions, for protecting not onlythe heater but to insure against producing a heated fluid of atemperature dangerously above or below the optimum value. 1

The construction and arrangement of the fluid heater here underconsideration, as well as its general mode of operation, is disclosed inthe copendlng. application of Ervin G. Bailey and Ralph M. .Hardgrove,Serial No. 502,580, now

Patent No. 2,447,306, to which reference may be had for a fullerexplanation of those features of construction and operation which arenot a part of the present invention. I

Our present invention particularly encompasses Bailey and Hardgrove.

certain preferred methods of an apparatus for "controlling the operationof such a fluid heater as is described in said copending application ofThe features of novelty which characterize our present invention arepointed out with particularity in the claims anneared to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which we'have illustrated and described preferred embodimentsof our invention.

In .the drawings:

Fig. 1 is an elevation, partly in section, of a" pilot plant unitconstructed in accordance with the invention of Bailey and Hardgrove,the structural supports being omitted for purposes of clarity.

Fig. 2 is a plan view of the apparatus shown in Fig. 1.

Fig. 3 is an "enlarged sectional elevation of a portion of the apparatusshown in Fig. 1.

Fig. 4 is a horizontal section taken on the line 4-4 of Fig. 3.

Fig. 5is an enlarged view of part of the apparatus shown in Fig. 3. 1

Fig. 6 diagrammatically illustrates one control system embodiment of ourinvention.

Fig. 7'is a sectional elevation, partially dia grammatic, of a pressuredifferential responsive device. I

Fig. 8 diagrammatically illustrates a further embodiment of a. controlsystem, including a showing of certain interlocks or protective devicesof the system.

Fig. 9 is a diagrammatic view of a three-element control system.

Figs, 1, 2, 3, 4 and 5 substantially duplicate tion is dapted for theuse of liquid and gaseous fluids as the heated and/or heating fluids,the method and apparatus of our invention are particularly adapted forthe use of high tempera- .ture gases as the heating fluid and a. gaseousfluid, such as a gas, vapor or finely divided solid in suspension, asthe fluid to be heated to a high temperature.

The heating unit illustrated in the drawings I is constructed anddesigned for the use of gaseous heating and heated fluids underpressure; p

fractory material is utilized for heating a second fluid, in the presentembodiment a gaseous fluid, to a predetermined temperature. An elevatorI2 is provided receiving the cooled refractory material from the lowerchamber II, returning it to the upper part of the upper chamber I0, anda control system providing automatic control means for regulatingoperating conditions in the system.

An annular combustion chamber M is provided having an annular passage 28comprising an outlet from the combustion chamber for the heated productsof combustion to the fluent mass of material I4. While various fuels canbeburned in the combustion chamber 2| to provide the de sired supply ofhigh temperature gases, or flue gases from other apparatus introduced asa source of heat, a gaseous fuel is used in the embodiment illustrated.Tangential burners are arranged in diametrically opposite parts of thecombustion chamber wall. An air supply connection 34 and a fuel supply38 provide the elements of combustion to' the burners. A valvecontrolled supply pipe 40 permits additional combustion air orrecirculated flue gas to be supplied in variable amounts for temperingthe heating gases generated.

The circular cross section of the upper'chamber I0 is progressivelydecreased to the upper end of a neck or throat passage 42 connecting thechambers Ill and II. The lower or heat absorb ing chamber I I is ofsubstantially uniform circular horizontal cross-section having near itslower end a valve controlled fluid inlet 52. A gaseous fluid outlet 54is formed in the upper part of the chamber I I above the normal level ofthe fluent mass' of material therein. The discharge of refractorymaterial from the chamber II is controlled by an adjustable inclinedgate 51 at the entrance of a variable speed fluid sealing materialdischarge device, such as a multi-pocket rotary feeder 59 driven by avariable speed electric motor 50 through a speed reducer 6|, as shown inFigs. 1 and 5. The fluent mass of material preferably moved at arelatively uniform rate downwardly through the chamber I0, the throat42, and the chamber I I, is desirably a high refractory material formedin pellets of approximately one-half inch in diameter.

The feeder 59 empties into the lower inlet of an elevator I2 returningthe pellets to the upper inlet pipe 28 of the chamber I0. Speed of thebuckets 51 may be controlled by varying the speed of the drivingelectric motor 68 or through variation of a gear reduction between thetwo.

In the normal operation of the apparatus described the chambers ID andII and throat 42 are filled with'refractory pelietsof the desired sizeand shape to approximately the levels indicated in Fig. 3. The fluentmass of pellets moves continuously downward through the upper chamber,throatpandlower chamber in series; at a 4 relatively slow ratecontrolled by the position of the gate 51 and the speed of the feeder59. The desired shape of these chambers and throat causes all portionsof the pellet column to move downwardly substantially continuously aslong as the feeder is in operation. Fuel is fired in the combustionchamber 2I and the heating gases generated flow throughthe annular inlet28 into the lower part of the upper chamber I0, passing upwardly throughthe interstices in the fluent mass in intimate counter-flow contact withthe descending pellets, whereby thepellets' are efficiently heatedto ahigh temperature and the gases leave through the heating gas outlet I8at a relatively low temperature. The highly heated pellets movedownwardly in a column through the throat 42 into the lower chamber II.The gaseous fluid to be heated, such as air, steam, naphtha, etc., isintroduced into the chamber II through the conduit 52 under apredetermined pressure, passing upwardly through the interstices betweenthe descending pellets in the chamber I I where it is heated incounterflow heat transfer, and passes out at the desired temperaturethrough the outlet 54. The pellets discharge through the feeder 59, areelevated by the elevator I2, and reenter the chamber III through theopening 20.

The relative pressure in the chambers III and II, as well as the flowbetween the chambers Ill and I I, or lack of flow, is controlled byprovisions disclosed in the'said Bailey and Hardgrove ap-' plication. i

As diagrammatically illustrated in Fig. ,6, the

" control system may include a differential pressure control responsiveto the pressure differential at vertically spaced points in or atopposite sides'of the throat 42 for regulating the exit of gaseous fluidfrom the upper or lower chamber to establish the desired relationbetween the pressure conditions in the two chambers. Damper regulationof the :heating gas outflow from the upperchamber is ordinarilypreferred, because of the lower temperature conditions at -that point.Differential pressure control apparatus diagrammatically illustratedcomprises a transmitter 80 responsive to the pressure differentialbetween the lower part of the upper chamber I0 and the fluid space atthe top of the lower chamber II, and a receiver recorder-controller 82.An air loading pressure is established by the controller 82representative of the pressure differential and III) is transmitted to astandardizing relay 83, which established a control pressure thentransmitted to a selector valve 84 and thence to a servo-motor arrangedto operate a damper I! in the heating gas outlet I8.

' .Th6 arrangement is such that upon a departure offthe pressuredifferential from the desired value an immediate and proportional changetakes place in the position of the damper I9 in direction' tending torestore the pressure condition in the upper chamber to the desiredrelative value. operates to gradually position the damper I8 until thepressure in the upper chamber reaches the predetermined desired value.The standardizing relay 83 is of a type described and claimed in Patent2,098,914 to Harvard H. Gorrie, whilethe selector valve 84 is describedand claimed in Thereafter the standardizing relay tive to coil windings209, 2"! and 2i I.

to manual control if that is desired in In Fig. 7 we illustrate thedevice an to larger scale. A particular problem presents itself inmeasuring or obtaining response to the pressurediiferential across thethroat 42 in that while the fluid in the chamber I is usually asubstantially dry flue gas the fluid within thechamber Ii may be acondensable vapor or gas, such for example as steam, naphtha, or thelike. Thus particular precautions must be taken in the design,construction and installation of the pressure differential responsivedevice 00 to prevent the possibility of error of measurement caused byfalse pressure heads produced by condensed vapor in the piping betweenthe point of connection to the chamber l I, and possibly in the device80 itself. Preferably the device 80 is located at or above the elevationof the pipe 20l connecting it to the chamber ii.

The device 80 is enclosed with a housing 203 capable of withstandingpressures of the order of fifty inches of water, although of course thedevice may readily be constructed to withstand higher pressures. Withinthe casing 203, and sealed thereto, is an expansible-contractiblemetallic bellows 204 dividing the interior of the housing 203 into twochambers 205 and 206. The pipe 200 connects the chamber i0 with thechamber 208, while the pipe 20l connects the chamber II with the chamber205.

Positioned by and with the bellows 204- is an extension arm 201carrying'at its upper end a magnetic core piece 208 positionable rela-The core 208 and windings 208, 2i0, 2|! cooperate to form thetransmitter of a telemetric system, such as is described and claimed inthe copending application of Anthony J. Hornfeck, Serial 453,488, nowPatent 2,420,539. While we have shown the windings onlydiagrammatically, it will be appreciated that they would probably beconstructed in the form of concentric or endto-end cylinders surroundingthe core piece 208. The pressure differentialacross the conthe desiredrate.

prising an orifice 2I4 disposed in the pipe ll, a differential pressureresponsive device 2!! responsive to the differential pressure producedby the orifice 2; and a pneumatic pilot valve generally indicated at2l0, which is actuated by the responsive device 2|! and acts toestablish an air loading pressure for positioning the'valve 2|3.

The pilot valve 2l0 may be of the type illustrated and described in theUnited States Patent 2,054,464 to Clarence Johnson and comprises astationary valve body 2" and a relatively movable valve member M0. Thevalve body 2i! is provided with a centrally located inlet port which maybe connected with any suitable source of air under pressure. The airentering the pilot valve passes into a longitudinally located passagewaypast suitable lands secured to the valve member M8 and is exhausted tothe atmosphere. The valve body 2" is also provided with an outlet port2i9, the pressure in which will be determined by the position of thelower land on the movable valve member 2I8, As the valve member 2l8moves downwardly the pressure established in the outlet port 2l9 willproportionately increase and conversely as the movable valve member 2l8moves upwardly the pressure established in the outlet port 2H! willdecrease. The pressure so established in the outlet port is transmittedto a pressure sensitive servo-motor 220 for operating the valve 213.Assuming, by way of example, that the flow of fuel through the pipe llincreases, the movable valve member 2l8 will be moved downwardly,thereby increasing the loading pressure in the outlet port 2 l0, andserving to position the valve 2 l 3 in a closing direction, therebytending to return the flow of fuel to A decrease in fuel flow will serveto position the valve member '2l8 upwardly, thereby decreasing theloading pressure effective on the servo-motor 220, positioning valve 2I3in an opening direction and again serving to nections 200 and 20l isbalanced by a spring 1 H2, which is initially under slighttension andtherefore able to move in tension or compression and allow theinstrument to work in either direction from a neutral or balancedcondition, namely. zero differential pressure relative to theatmosphere. In other words, the instrument is responsive to a plus orminus pressure differential between the chambers l0 and ii, therecording pen of the instrument 82 has its zero part way up on the chartand thus will indicate whether or not the pressure in the throat 42 isbalanced, or whether there is a slight flow upwardly or downwardly fromone chamber to the other. g

In Fig. 6 we illustrate one embodiment of our invention including aconstant flow control of the fuel fired to the combustion chamber 2|,with the standard of the constant flow control established bytemperature of the vapor leaving the chamber ll through the conduit 54.The principal purpose of the control is'to maintain vapor outlettemperature at ,a predetermined value, returning it to such value upondeparture return the fiow of fuel to the desired valve.

The movable valve member 2 I 8 is also arranged to be positioned by acam 22l,- which serves to establish the desired rate of fuel flowthereafter maintained by the constant flow control. In accordance withour invention the cam 22I is automatlcally positioned by meansresponsive to the temperature'of the vapor leaving the chamber llthrough the conduit 54 to maintain the temperature of the leaving vaporat a predetermined or desired value. The constant flow control servesthe purpose of correcting for changes in the rate of fuel flow, due tovariations in fuel pressure, etc. before such changes cause undesirablechanges in the temperature of the vapor In general, it maybe rotating,is in series with either the winding 223 or the winding 224, dependingupon the dcsired direction of rotation. Such amotor runs as a two-phasealternating current motor, and 1 not only may be reversed as todirection of rotation, but is susceptible of speed control when totating in either direction. While in the present cally shown. as locatedin a well or socket in the I conduit 54' and has an electricalresistance value varying with temperature of the vapor or fluid leavingthe chamber I I through the conduit 54.

- Thus the resistance 221 constitutes a variable resistancerepresentative of temperature and forming one arm of the bridge 226.Hand adjustable resistances 226 and 229 provide means for callbratingand adjusting the circuit including the alternating current Wheatstonebrid The hand adjustable resistance 230 including an in,-

dicating scale "I, provides a ready means for establishing thetemperature standard (of the Variations in electrical resistance of theelement 221 (produced by variations in temperature of the vapor outflow)results in an' unbalance of the bridge 226 as to polarity or phase ofthe current in the conjugate conductor 232, with respect to the polarityor phase of the current produced by the source 231. We employ thischange in polarity or phase, through an amplifler 231, to selectivelyoperate the motor 222 in one direction or the other to vary the positionof the cam 22l.

We have shown the mechanical connection between the motor 222 and cam22l diagrammatically, it being understood that suitable reducing gears,etc. may be employed so that the cam MI is normally positioned betweensuitable angular limits of less than 360 over the operating range of thecontrol apparatus. When the temperature of the outflowing vapor (asreflected by the resistance value 221) is at the desired value then thecam 22l will be in predetermined position and the system in equilibrium.

' Should the rate of supply of fuel through the conduit 10 vary for anyreason, such for example as variations in supply pressure, then thepressure differential responsive device 2 l 5 will position the pilotstem 218 to slightly increase or decrease the store the temperature tothe desired value. Thus the system will not tend to stabilize out atsome vapor outflow temperature other than the desired temperature.

In general the control system provides a constant flow control of thefuel flred to the combustion chamber 2|, reset from vapor outflowtemperature, to maintain vapor outflow temperature at a predeterminedvalue. The embodiment described in connection with Fig. 6 provides for avery speedy response in heat input to the pellets following anydeviation in fuel supply rate or any deviation of vapor outflowtemperature from desired temperature through any cause whatsoever. I

In Fig. 8 we illustrate another embodiment of our invention, which ingeneral utilizes vapor outflow temperature as a controlling factor forsimultaneous control of the rate of supply of fuel to the combustionspace 2| and of the rate of circulation of the pellets through a controlof the speed of the pellet feeder 59. As we have previ- 'ously pointedout, the temperature of the vapor vapor outflow) which the system is tomaintain.

leaving the chamber ll may be varied either. by varying the firing andthereby the temperature to which the pellets are heated, orby varyingthe speed of circulation of the pellets from the chamber-d0 to andthrough the chamber II and thereby the rate of heat transfer from thepellets to the vapor passing through the chamber I I. In order that acheck may be kept upon the temperature to which the pellets themselvesare raised, we provide means sensitive to the temperature of the pelletsfor resetting the control valve in the fuel gas supply line.

The resistance thermometer, including the temperature sensitive element221, is similar to that described in connection with Fig. 6 whereindepartures of vapor outflow temperature from predetermined optimumtemperature effect a rotation of the motor 222 in one direction or theother. The motor 222 mechanically positions one end of a floating link239 through necessary gear or linkage reduction. The motor 222 also isconnected to position the movable element of a motor control rheostat240 regulating'the speed of the motor 60 which drives the feeder 59. Itis apparent that the motor 222 might equally as well I 59. Thus it willbe seen that the motor 222, senopening of the control valve 2l3, therebycorre'ctvalue which is desirably to be maintained con-- stant. This isthe operation for any fixed position of the cam 22l representative of apredetermined temperature of the vapor outflow past the resistance 221.

Should the vapor outflow temperature vary in one direction or the otherfrom the desired standard (assuming that the rate of supply of fuel hasremained constant) then the consequent variation in resistance 221, andunbalance of the bridge 226 thereby, will result in the motor 222positioning the cam 22! to slightly raise or lower, the pilot stem 2i!and control the valve 2i3'to correct the rate of fuel supply to overcomethe deviation of vapor outflow temperature from desired temperaever theactual temperature is other than that desired the rate of application ofthe corrective agent (fuel) is varied in direction tending to resitiveto temperature of the vapor outflow through the conduit 54, issimultaneously effective in varying the rate of feed of the pellets outof the chamber ii and upon the control valve 2 l3 for the fuel supply tothe combustion chamber 2|.

We provide a radiation pyrometer having a temperature sensitive element24! arranged to look at the pellets in the throat 42. We believe thatthis is a logical place to obtain pellet temperature, although we mightdesire to arrange the radiation element 24I to look at the pellets atsome point in the chamber l0 above the throat 42 or at some point in thechamber ll below the throat 4'2 Without limiting the scope of ourinvention.

For positioning the other end of the floating link 236 we provide amotor :242 having opposed pole windings 243 and 244 controlled bydifferentially regulating the reactance of 'a circuit in which they areincluded. Connected in, circuit with the pole winding 243 is a condenser245 and the output winding 246 of asaturable core reactor 241. winding244' is a condenser 248 and the output Connected in circuit with thepole presents a very serious problem. a

winding 249 of a saturable core reactor 250, The reactor 241 is providedwith a control winding 25l and a separately excited adjustable biaswinding 252.

The control windings 25l and 253 are connected in series to the device 2which produces. a potential corresponding to the temperature of thepellets. While we have-shown the photoelectric device 24l as comprisinga photovoltaic cell disposed to look at the pellets within the throat 42and producing a potential corresponding to the radiation emanatingtherefrom, it is evident that equivalent means such as a. thermocoupleor thermo-pile could be employed. The particular arrangement andfunctioning of the circuit utiliz- The reactor 25!! is similarlyprovided with. a control winding 253 and a'bias winding 254 connected inparallel with the bias winding 252.

the conduit 52 decreases below a predetermined m inimum., We illustratethe motor 242, positioned responsive to the radiation pyrometer. beingadapted to actuate a mercury switch 252 to open an electric circuit whenthe temperature of the pellets reaches a predetermined high value.

- In Fig. 8 we have shown the system in a non-' ing said potential incontrol of the motor 242 isdescribed and claimed in Patent 2,310,955 toHornfeck.

A particular advantageof using the radiation type pyrometer, which wehave described is that it will have a considerably greater life, thanany thermocouple or resistance thermometer or other temperaturesensitive element which might be of necessity inserted directly into themoving column of pellets. The temperature is extremely operatingcondition with the "hand actuated switches 215 and 211 open, thesolenoid valve 255 deenergized and closed, and no flow of liquidentering through the conduit 52. The relay 215 is deenergized and opencircuited. The relays 255 and 251 are deenergized and open circuited.Pressure of the air for combustion is below a predetermined minimum sothat the mercuryswitch 259 is open circuited. The mercury switches 2"and 252 are both sh'own'in open oircuited condition.

In'general, the solenoid valve 255 is normally ating conditions theheating, as represented by high and the abrasive action of refractorypellets In'F'ig. 8 we have also illustrated schematicall a combinationof interlocks which we have felt it advisable to provide in theoperation of this type stoppage of circulation of the pellets throughthe chambers l0 and I I, it is desirable thatthe heating bediscontinued.

2. Should the supply of vapor to the chamber ll be interrupted, then theheating should be diminished or discontinued and the feeder stopped,

3. Should the pressure of the air supplied for combustion decrease belowa predetermined minimum then the heating should be discontinued.

4. Should the elevator stop, and thus the circulation of pelletsbeinterrupted, the heating should be discontinued and the feeder stopped.

5. If the pellet temperature, as measured by the radiation pyrometer,reaches an upper limit, then the heating shouldbe discontinued.

A practical way of discontinuing the heating is, of course, to shut offthe supply of fuel through the conduit 38 to the combustion chamber 2|.We therefore show positioned in the fuel line 38 a solenoid actuatedvalve 255 adapted to shut off the supply of fuel to the furnace when thesolenoid is deenergized.

In the control circuit of the feeder motor 50' we illustrate a relay 256adapted to become deenergized and thus open a circuit when the motor 50is not receiving running current. In the mo-, tor circuit ofthe elevatormotor we illustrate a solenoid arranged to be deenerglzed and thus opena circuit when the elevator motor is not receiving running current.Connected to the air the supply of fuel to the furnace, will bediscontinued and avoid a dangerous temperature condition within the 42.

Under certain conditions it is desirable to stop the pellet feeder 58and we have therefore included a relay 215 in the control circuit of themotor 50. Under normal operating conditions the circuit closer of therelay 215 is at closed circuit position. In the event of emergencycondition then the relay 215 becomes deenergized and the motor controlcircuit for the motor 80 is opened. In order that the motor 60 may bestart fed by hand we provide a switch 215 by-passing supply pipe 34 Weillustrate a Bourdon tube 258 sensitive to pressure of the air and formechanically actuating a mercury switch 259 to open the circuit of saidmercury switch when the air pressure decreases below a certain value. Wehave indicated in connection with the vapor supply the relay contact215.

At21'l we provide a hand switch for holding chambers III or II or thethroat open the solenoid valve 255 in the fuel supply fluid leaving thechamber H after it has been heated.

A differential pressure responsive device 218, similar to the device 2|5of Fig. 6, is arranged to position the pilot valve 219 to establish aloading pressure representative of the rate of supply of fuel to thecombustion chamber 2|.

2811 establishes .a loading pressure representative ofnthe rate ofsupply onfluid to the chamber ll through the conduit 52.

In similar manner a'difl'erential pressure responsive device The loadingpressures mentioned are transmitted to a ratio relay 28l producing aloading pressure in the pipe 282 representative of the relation between,or ratio of. the two rates of flow.

Such loading pressure is effective within a chamber of the standardizingrelay 283. To this relay is also conducted a loading pressure estab- Ilishedby the pilot 284 representative of tem-' perature of the fluidleaving the chamber ll through the conduit 54. The pilot 254 ispositioned by a motor 285 'under the control of an electrical networkincluding a thermocouple 255.

- 11 The thermocouple circuit for control of the motor 288 may be aknown potentiometer and amplifying circuit.

From the standardizing relay 288 the loading pressure. is effective(through a selector valve 281) in positioning a control valve 288regulating the rate of supply of fuel to the combustion chamber 2|.

In general, the system illustrated in Fig. 9 balances the'rate ofsupply-of fuel (for heating the pellets in the chamber HI) against therate of supply of fluid to be heated entering the chamber i I throughthe conduit 52. If the B. t. u. value of the fuel, the temperature ofthe fluid entering through the conduit 82, and other variables remainconstant, then the rate of supply of fuel proportioned to the rate ofsupply of fluid to be heated could adequately regulate the valve 288.

The tie-back, or third element, in the system is the use of the finalresult, namely, temperature By modifying the control of thevalveporatedn the control of the valve 288 any modtemperature rangeexpected.

" While we have illustrated and described certain preferred embodimentsof our invention, it will be understood that these are illustrative onlyand that the salient features of the invention may be-carried out inother manner and with other apparatus than those specifically described.

Certain features of our invention, disclosed but not claimed herein, aredisclosed and claimed in our copending divisional application Serial No.715,044, filed Dec. 9, 1946.

What we claim as new, and desire to secure I by Letters Patent of theUnited States, is:

1. The combination with a fluid heater having an upper chamber enclosinga fluent mass of refractory pellets, a lower chambenenclosing' a fluentmass of refractory pellets, a passage forming a throat of reducedcross-section between said upper and lower chambers and enclosing acolumn of refractory pellets connecting said masses, means external ofsaid chambers and throat arranged to return pellets from an exit -in thelower chamber to an inlet to the upper chamber, a fuel supply means forheating the pellets inthe upper chamber, a supply of fluid to beheatedpassing through the lower chamber in direct contact with theheated pellets therein,- and means vregulating the fuel supply rateresponsive to both heated fluid temperature and temperature of theheated pellets.

2. The combination with a fluid heater having an upper chamber enclosinga fluent mass of solid material, a lower chamber enclosing a fluent massof solid material, a passage forming a throat of reduced cross-sectionbetween said upper and lower chambers and enclosing a column of fluentsolid material connecting said masses, means external of said chambersand throat arranged to return said material from an exit in the lowerchamber to an inlet to the upper chamber, a fuel supply means forheating the solid material in I 12 the upper chamber, a supply of fluidto be heated passed through the lower chamber in direct contact with theheated material therein, and means regulating the fuel supply rateresponsive to temperature of the solid material leaving the upperchamber.

3. The combination with a fluid heater having an upper chamber enclosinga fluent mass of re fractory pellets, a lower chamber enclosing a fluentmass of refractory pellets, a passage forming a throat of reducedcross-section between said upper and lower chambers and enclosing acolumn of refractory pellets connecting said masses, means external ofsaid chambers and throat arranged to return pellets from an exit in thelower chamber to an inlet to the upper chamber, a fuel supply means forheating the pellets in the upper chamber, a supply of fluid to be heatedpassed through the lower chamber in direct contact with the heatedpellets therein, means regulating the fuel supply rate responsive toboth heated fluid temperature and temperature of. the heated pellets,and means regulating the rate of movement of the pellets from the upperto the lower chamber responsive to temperature of the 'heated fluidleaving the lower chamber.

4. The combination with a fluid heater'having "an upper chamberenclosing a fluent mass of refractory pellets, alower chamber enclosinga fluent mass of refractory pellets, a passage forming a throat ofreduced cross-section between said upper and lower chambers and enclosina column of refractory pellets connecting said masses, means external ofsaid chambers I and throat arranged to return pellets from an exit inthe lower chamber to an inlet to the. upper chamher, a feeder at theexit of the lower chamber feeding pellets at a regulable rate fromthelower chamber to the returning means, a heating supply for thepellets in the upper chamber, a supply of fluid to be heated passingthrough the lower chamber in direct contact with the heated pelletstherein, and means sensitive to the temperature of the fluid leaving thelower chamber adapted to regulate the feeder speed.

5. The combination of claim 4 including means sensitive to adiscontinuance of feeder operation adapted to discontinue the heatingsupply.

6. The method of operating apparatus having an upper chamber enclosing afluent mass of solid material, a lower chamber enclosing a fluent massof solid material, and a throatof reduced cross-section connecting theupper and lower chambers and enclosing a fluent mass'of the solidmaterial connecting the upper and lower chamber masses; which includesmaintaining a substantially continuous flowof solid material downwardlythrough the upper chamber, throat and lower chamber, continuouslysupplying a heating medium to the upper chamber in direct contact withthe solid material therein, continuously supplying a fluid to be heatedto the lower chamber in direct contact with the mass of solid materialtherein, and controlling the rate of supply of the heating mediumresponsive to temperature of the heated solid material.

'7. The method of operating apparatus having an upper chamber enclosinga. fluent mass of solid material, a lower chamber enclosing a fluentmass of solid material, and a throat of reduced cross-section connectingthe upper and lower chambers and enclosing a fluent mass of the solidmaterial. connecting the upper'and lower chamber masses: which'includesmaintaining a substantially .continuous flow of solid material materialtherein, and controlling therate of 'sup-.

by contact with the material in the lower chambers and to temperature ofthe heated material.

8. The methodof operating apparatus having an upper chamber enclosing afluent mass oi solid material, a lower chamber enclosing a fluent I massof solid material, and a throat of reduced cross-section connecting theupper and lower chambers and enclosing a fluent mass of the solidmaterial connecting the upper and lower chamber masses; which includesmaintaining a substantially continuous flow of .solid materialdownwardly'through the upper chamber, throat and lower chamber,continuously supplying -a 'ply of the heating medium Jointly responsiveto temperature of the fluid after it has been heated sacs? 14 secondchamber and exteriorly from thesecond chamber back to the first chamberincluding; maintaining ,a supply of heating medium to the. flrst chamberto heat the material as it passes j therethrough, passing a fluid to beheated through the-second chamber in direct contact with the heatedmaterial passing therethrough, regulating the rate of supply of theheating medium responsive to temperature of the heated fluid, andautomatically stopping the heating upon occurrence of i an interruptionto material movement through the heating medium to the upper chamber indirect contactwith the solid material therein. continuously supplying aflu d to be heated to the lower chamber in direct contact with the solidmaterial therein, and utilizing the temperature otthe'fiuidv afterit hasbeen heated to coniointly control the rate of supply of heating mediumand the rate of downward flow of the solid material.

9. The method of operating apparatus having an upper chamber enclosing afluent mass oi' so id material, a lower chamber enclosing a fluent mass'of solid material, and a throat of reduced. crosssection connecting theupper and lower chambers .1 and enclosing a fluent mass oi' the solidmaterial connecting the upper and lower chamber mass s: which includesmaintaining a substantally continuous flow of solid material downwardlythrough the upper chamber, throat and lower chamber continuouslysupplying a heating medium to the upper chamber in direct contact withthe solid material therein, continuously supplying a fluid to be heatedto the lower'chamber in direct contact with the solid material therein,utilizing the temperature of the fluid after it has been heated toconiointly control the rate of supply of heating medium and the rate ordownward movement of the solid material, and modifying the control ofthe supply of heating medium responsive to temperature of the heatedsolid material.

10. The method of operating a fluid heater 0! the type having twochambers connected by a chambers and in the throat and having provisionforsubstantialiy continually moving such material i'rom the firstchamber-through the throat to throat with heat transfer material in eachof the system.

12. The method of operating a fluid heater of the type having twochambers connected by a throat with heat transfer material in each ofthe chambers and in the throat and having provision for substantiallycontinually moving such material from the first chamber through thethroat to the second chamber and exteriorly from the second chamber backto the first chamber,- including, maintaining a supply of heating mediumto the first chamber to heat the material as it passes therethrough,passing a fluid to be heated through the second chamber in directcontact with the lntated material passing therethrough, regulating therate of supply of the heating medium responsive totemperature of theheated fluid, and automatically stopping the supply of heating mediumwhen the rate of supply of the fluid decreases to a predeterminedminimum.

13. The method of operating a fluid heater of f the type-having twochambers connected by a throat with heat transfer material in each oithe chambers and in the throat, and-havlng provision for substantiallycontinually moving such material from the first chamber throughthethroat to the second chamber and exteriorly from the second chamber backto the first chamber, including, maintaining a supply or heating mediumto the first chamber to heat the material as it passes therethrough,passing a fluid to be heated through the second chamber in directcontact with the heated material passing therethrough, regu lating therate of supply of the heating medium responsive to temperature vof theheated fluid, and automatically discontinuing both the supply of heatingmedium and the movement of the heat transfer material through the systemwhen "the rate of supply of the fluid decreases to a predeterminedminimum. i

14. The method .of operating a fluid heater of the type having twochambers connected by a ,throat with heat transfer material in each ofthe chambers and in the throat and havingprovision for substantiallycontinually moving said material from the flrst chamber through thethroat'to the.

- second chamber and exteriorly from the second the second chamber .andexteriorly from the second chamber back to the first chamber including,maintaining a supply of heating medium to th flrst chamber to heat thematerial as it passes therethrough, passing a fluid to be heated throughthe second chamber in direct contact with the heated material pass ngtherethrough, regulating the rate of supply of the heating mediumresponslve to temperature of the heated fluid, and automaticaliystopping the supply of heating medium under any one oi severalredetermined emergency conditions.

11. A method of operating a fluid heater of the type having two chambersconnected by a throat with heat transfer material in each of thechambers and in the throat and having provision for substantiallycontinually moving such material from the first chamber through thethroat to the chamber back to the first chamber, including, maintaininga supply of heating medium to the first chamber to heat the material asit passes therethrough, passing a fluid to be'heated through the secondchamber in direct contact with the heatedmaterial passing therethrough,regulating the rate of supply of the heating medium responsive totemperature of the heated fluid, and automatically discontinuing theheating when a vari- T able condition of the heating medium'decreasesbelow a minimum value.

15. The m-ethod of operating a flu'd heater of the type having twochambers connected by a solid heat transfer material, a lower chamberenclosing a fluent mass of solid heat transfer matei rial, a passageforming a throat between said upper and lower chambers and enclosing afluentmass of solid heat transfer material connecting said materialmasses, means extemal of said chambers and throat to return the materialfrom an exit in the lower chamber to an inlet to the upper chamber, afeeder at the exit of the lower chamber feeding material at a regulablerate from the lower chamber to the returning means, a

' heating supply for the material in the upper 16. The method ofoperating a fluid heater of' the type having two chambers connected by athroat with heat transfer material in each of the chambers and in thethroat and having provision for substantially continually moving suchmaterial from the first chamber through the throat to the second chamberand exteriorly from the second chamber back to the first chamber,including, maintaining a supply of beating medium to the first chamberto heat the material as it passes therethrough, passing a fluid to beheated through the second chamber in direct contact with the heatedmaterial passing there through, regulating the rate of supply of theheating medium responsive to temperature ofthe heated fluid, andautomatically discontinuing both the heating and the movement of heattransfer material through the heater upon occurrence of an interruptionto movement of the heat transfer material exteriorly from the secondchamber back to the first chamber.

17. The method of operating a fluid heater of the type having twochambers connected by a throat with heat transfer material in each ofthe chambers and in the throat and having provision for substantiallycontinually moving such mate rial from the first chamber through thethroat to the second chamber and exteriorly from the second chamber backto the first chamber, including, maintaining a supply of heating mediumto the first chamber to heat the material as it passes therethrough,passing a fluid to be heated through the second chamber in directcontact with the heated material passing therethrough, regulating therate of supply of the heating medium responsive to temperature of theheated fluid, and automatically discontinuing the heating when thetemperature of the heat transfer material leaving the first chamberexceeds a predetermined value.

18. The combination with a fluid heater having an upper chamberenclosing a fluent mass of solid heat transfer material, a lower chamberenclosing a fluent mass of solid heat transfer material, a passageforming a throat between said upper and lower chambers and enclosing afluent massof solid heat transfer material connecting said materialmasses, means external of .said chambers and throat to return thematerial from chamber, a supply of fluid to be heated passed through'thelower chamber in direct contact with the heated material therein, meanssensitive to the temperature of the fluid leaving the lower chamberadapted to regulate the rate of heating supply, and means responsive tothe rate of supply of the fluid adapted to discontinue the heatingsupply when the rate of supplyof the fluid to be heated decreases to apredetermined minimum.

20. The combination with a fluid heater having an upper chamberenclosing a fluent mass of solid heat transfer material, a lower chamberenclosing,a fluent mass of solid heat transfer material, a passageforming a throat between said upper and lower chambers and enclosing afluent mass ofsolid ,heat transfer material connecting said materialmasses, means external of said chambers and throat to return thematerial from an exit in the lower chamber to an inlet to the upperchamber, a feeder at the exit of the lower chamber feeding material at aregulable rate from the lower chamber to the returning means, a heatingsupply for the material in the upper chamber, a supply of fluid to beheated passed through the lower chamber in directcontact with the heatedmaterialtherein, means sensitive to the temper- 21. The combination witha fluid heater having an upper chamber enclosing a fluent mass of solidheat transfer material, a lower chamber enclosing a fluent mass of solidheat transfer material, a passage forming a thrbat between said upperand lower chambers and enclosing a fluent mass of solid heat transfermaterial connecting said material masses, means external vof saidchambers and throat to return the material from an exit in the lowerchamber to aninlet to the upper chamber, a feeder at the exit of thelower chamber feeding material at a regulable rate from' the lowerchamber to the returning means,

an exit in the lower chamber to an inlet to the 7, upper chamber, afeeder at the exit of the lower chamber feeding material at a regulablerate from the lower chamber to the returning means, a heating supply forthe material in the upper chamber, a supply of fluid to be heated passedthrough the lower chamber in direct contact with the heated materialtherein, means sensitive to a heating supply for the material in theupper chamber, a supply-of fluid to be heated passed condition of theheating adapted to discontinue the heat ng supply when the value of sa dvariabe decreases below a predetermined minim m.

22. The combination with a fluid heater having an upper chamberenclosing a fluent mass of solid heat transfer material, a lower chamberenclosing a fluent mass of solid heat transfer material, a passageforming a throat between said a heating supply for the material in theupper chamber, a supply of fluid to be, heated passed through the lowerchamber in direct contact with the heated material therein, meanssensitive to the temperature of the fluid leaving the lower chamberadapted to regulate the rate of heating supply, and means sensitive toan operating condition of the returning means adapted to discontinue theheating upon failure of the returning 18 chambers and throat to returnthe material from an exit in the lower chamber to an inlet to the upperchamber, a feeder at the exit, of the lower chamber feeding materialat aregul'able rate from the lower chamber to the returning means and"thereby determining the downward movement means to return materialexteriorly from the exit of the second chamber to the entrance of thefirst chamber.

23. The combination with a fluid heater having an upper chamberenclosing a, fluent mass of solid heat transfer material, a lowerchamber enclosin a fluent mass of solid heat transfer material, apassage forming a throat between said upper and lower chambers andenclosing a fluent ternal of said chambers and throat to return the massof solid heat transfer material connecting said material masses, meansexternal of said chambers and throat to return the material from an exitin the lower chamber to an inlet to the upper chamber, a feeder at theexit of the lower chamber feeding material at a regulable rate from thelower chamber to the returning means,

a heating supply for the material in the upper chamber, a supply offluid to be heated passed through the lower chamber in direct contactwith the heated material therein, means sensitive to the temperature ofthe fluid leaving the lower chamber adapted to regulate the rate ofheating supply, and means sensitive to a function of operation of thereturning means adapted to discontinue the heating supply and to stopthe feeder when the returning means ceases to function.

24. The combination with a fluid heater havin an upper chamber enclosinga fluent mass of solid heat transfer material, a lower chamber enclosinga fluent mass of solid heat transfer material, a passage forming athroat between saidupper and lower chambers and enclosing a fluent massof solid heat transfer material connecting said material masses, meansexternal of said chambers and throat to return the material from an exitin the lower chamber to an inlet to the upper chamber, a feeder at theexit of the lower chamber feeding material at a regulable rate from thelower chamber to the return.- ing means, a heating supply for thematerial in the upper chamber, a supply of fluid to be heatedpassedthrough the lower chamber in direct contact with the heatedmaterial therein, means sensitive to the temperature of the fluidleaving the lower chamber adapted to regulate the rate of heatingsupply, and means sensitive to temperature of the heat transfer materialadapted to discontinue the heating supply when the temperature of theheat transfer material exceeds a predetermined value.

25; The combination with a fluid heater having an upper chamberenclosing a fluent mass of solid heat transfer material, a lower chamberenclosing a. fluent mass of solid heat transfer material, a passageforming a throat between said upper and lower chambers and enclosing afluent mass of solid heat transfer material connecting said materialmasses, means external of said of heat exchange material through theupper chamber and throat and lowerchamber, a heatin supply for thematerial in the upper chamber, a supply of fluid to be heated passedthrough the lower chamber in direct contact with the heated materialtherein, and means sensitive to the temperature of the fluid after ithas been heated adapted to conjointly control the heating supply meansand the feeder.

26. The combination with a fluid heater having an upper chamberenclosing a fluent mass of solid heat transfer material, a lower chamberenclosing a fluent mass of .solid heat transfer material, anunobstructed passage forming a throat between said upper and lowerchambers and enclosing a fluentmass of solid heat transfermaterialconnecting said material masses, means exmaterial from an exit in thelower chamber to an inlet to the upper chamber, a feeder at the exit ofthe lower chamber feeding material'at a regulable rate from the lowerchamber to' the returning means, a, heating supply for the material inthe upper chamber, a supply of fluid to be heated passed through thelower chamber in direct contact with the heated material therein, saidheating supply comprising the products ofcombustion of fuel and air,a-supply of fuel for combustion, a supply of air for combustion, and

means sensitive to the temperature of the fluid leaving the lowerchamber adapted to con1oin'tly control the rate of supply of fuel forcombustion and said feeder. k

27. The combination with a fluid heaterhaving an upper chamber enclosinga fluent mass of solid heat transfer material, a lower chamber enclosina fluent mass of solid heat transfer material, an unobstructed passageforming a throat between said upper and lower chambers and enclosing afluent mass of solid heat transfer ma! terial connecting said materialmasses, means external of said chambers and throat to returnthe materialfrom an exit in the lower chamber to an inlet to the upper chamber, a,feeder at the exit of the lower chamber feeding material at a regulablerate from the lower chamber to-the returning means, a heating supply forthe material in the upper chamber, a supply of fluid to-be heated passedthrough the lowerchamber in direct contact with the heated material,therein, said heating supply comprising the products of combustion,supply means for the elements of combustion, and means sensitive to thetemperature of the fluid leaving the lower chamber adapted to regulatethe rate of supply of at least one of the elements of combustion andsimultaneous- 1y to control the feeder. I

28. The method of operating a fluid heater of the type having twochambers connected by a throat withheat transfer material in each of thechambers and in the throat and havin provision for substantiallycontinually moving such sponsive to a measure of the temperature of theheated fluid leaving the lower chamber.

29. The method of operating a fluid heater of the type having twochambers connected by a throat with heat transfer material in each ofthe chambers and in the throat and having provi- H sion forsubstantially continually moving such material from the fl'rst chamberthrough the throat to the second'chamber and exteriorly from the secondchamber back to the flrst chamber,.

including, maintaining a supply of heating medium tothe first chamber toheat material as it passes therethrough, passing a fluid to be heatedthrough the second chamber in direct contact with the heated materialpassing therethrough, and regulating the speed of movement of the heattransfer material through the system responsive to the temperature ofthe fluid after it has been heated;

30. The combination with a fluid heater having an' upper chamberenclosing a fluent mass of refractory pellets, a lower chamber enclosinga fluent mass of refractory pellets, a passage form'- ing a throat ofreduced cross-section between said upper and lower chambers andenclosing a column of refractory pellets connecting said masses, meansexternal of said chambers 'and throat arranged to return pellets from anexit in the lower chamber to an inlet to the upper chamber, a feeder atthe exit of the lower chamber feeding pelletsat a reguiable rate fromthe lower chamber to the returning means, a heating supply for thepellets in the upper chamber, a supply of fluid to' be heated passingthrough the lower chamber in direct contact with the heated pelletstherein, and means sensitive to the temperature masses, means externalof said chambers and throat arranged to return pellets from an exit inthe lower chamber to an inlet to the upper chamber; a regulable meansfor varying the rate of return of pellets from the lower to the upperchamber, a heating supply for the pellets in the upper chamber, a supplyof fluid to be heated assing through the lower chamber in direct contactwith the heated pellets therein, and means sensitive to the temperatureof the fluid at a predetermined location in it flow path and adapted tocontrol the regulable means.

33. The method of operating a fluid heater of the type having twochambers connected by a throat with heat transfer material in each ofthe chambers and in the throat and having provision for substantiallycontinually moving such material from the first chamber through thethroat tothe second chamber and exteriorally from the second chamberback to the first chamber; including maintaining a supplyof heatingmedium to the flrst chamber-to heat material as it passes therethrough,passing a fluid to be heated through the second chamber in directcontact with the heated material passing therethrough, and regulatingthe speed of movement of the heat transfer material through the systemresponsive to the temperature of the fluid at a predetermined location.r

34. A continuous process for effecting thermal treatment of gases atelevated temperatures which comprises continuously flowing by gravity afluent mass if hot refractory pellets through a series of substantiallyvertically extending zones comprising a pellet heating zone and a gasheating zone; continuously contacting that portion of said mass ofpellets in said pellet heating zone with a stream of hot combustion gas,thereby substantially heating said pellets; continuously contacting thatportion of said mass of pellets in said gas heating zone with acountercurrent stream of gas to be heated, thereby heating said gas asubstantial amount; and continuously transferring pellets from the lowerportion of said gas heating zone to the upper portion of said pelletheating zone at a rate regulated in response to variations intemperature of the gas being heated.

35. A continuous process for effecting thermal treatment of gases atelevated temperatures which comprises continuously flowing .by gravity afluent mass of hot refractory pellets through a series of subsantiallyvertically extending zones comprising a pellet heating zone and a gasheating zone; continuously contacting that portion of said mass ofpellets in said pellet heating zone with a stream of hot combustion gas,thereby substantially heating said pellets; continuously contacting thatportion of said mass of pellets in said gas heating zone with acountercurrent stream of the gas to be heated, thereby heating said gasa substantial amount; continuously transferring pellets from the lowerportion of said gas heating zone to the upper portion of said pelletheating zone; and varying the operation in response to variations inpellet temperature.

ERVIN G. BAILEY. PAUL S. DICKEY.

No references cited.

